for Journals by Title or ISSN
for Articles by Keywords
help
  Subjects -> ENGINEERING (Total: 2170 journals)
    - CHEMICAL ENGINEERING (186 journals)
    - CIVIL ENGINEERING (168 journals)
    - ELECTRICAL ENGINEERING (92 journals)
    - ENGINEERING (1177 journals)
    - ENGINEERING MECHANICS AND MATERIALS (356 journals)
    - HYDRAULIC ENGINEERING (56 journals)
    - INDUSTRIAL ENGINEERING (54 journals)
    - MECHANICAL ENGINEERING (81 journals)

CHEMICAL ENGINEERING (186 journals)                  1 2     

AATCC Journal of Research     Full-text available via subscription   (Followers: 2)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 10)
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials     Hybrid Journal   (Followers: 4)
Acta Polymerica     Hybrid Journal   (Followers: 6)
Additives for Polymers     Full-text available via subscription   (Followers: 21)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 5)
Advanced Chemical Engineering Research     Open Access   (Followers: 9)
Advanced Powder Technology     Hybrid Journal   (Followers: 16)
Advances in Applied Ceramics     Partially Free   (Followers: 3)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 17)
Advances in Chemical Engineering and Science     Open Access   (Followers: 23)
Advances in Polymer Technology     Hybrid Journal   (Followers: 11)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 5)
Annual Review of Analytical Chemistry     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 11)
Anti-Corrosion Methods and Materials     Hybrid Journal   (Followers: 5)
Applied Petrochemical Research     Open Access   (Followers: 3)
Asia-Pacific Journal of Chemical Engineering     Hybrid Journal   (Followers: 6)
Biochemical Engineering Journal     Hybrid Journal   (Followers: 9)
Biofuel Research Journal     Open Access  
Biomass Conversion and Biorefinery     Partially Free   (Followers: 6)
BMC Chemical Biology     Open Access   (Followers: 4)
Brazilian Journal of Chemical Engineering     Open Access   (Followers: 3)
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Carbohydrate Polymers     Hybrid Journal   (Followers: 9)
Catalysts     Open Access   (Followers: 7)
Chemical and Engineering News     Free   (Followers: 5)
Chemical and Materials Engineering     Open Access   (Followers: 1)
Chemical and Petroleum Engineering     Hybrid Journal   (Followers: 9)
Chemical and Process Engineering     Open Access   (Followers: 3)
Chemical and Process Engineering Research     Open Access   (Followers: 5)
Chemical Communications     Full-text available via subscription   (Followers: 31)
Chemical Engineering & Technology     Hybrid Journal   (Followers: 23)
Chemical Engineering and Processing: Process Intensification     Hybrid Journal   (Followers: 10)
Chemical Engineering and Science     Open Access   (Followers: 3)
Chemical Engineering Communications     Hybrid Journal   (Followers: 10)
Chemical Engineering Journal     Hybrid Journal   (Followers: 21)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 16)
Chemical Engineering Research Bulletin     Open Access  
Chemical Engineering Science     Hybrid Journal   (Followers: 13)
Chemical Geology     Hybrid Journal   (Followers: 11)
Chemical Papers     Hybrid Journal   (Followers: 3)
Chemical Product and Process Modeling     Hybrid Journal   (Followers: 3)
Chemical Reviews     Full-text available via subscription   (Followers: 167)
Chemical Society Reviews     Full-text available via subscription   (Followers: 33)
Chemical Technology     Open Access   (Followers: 5)
ChemInform     Hybrid Journal   (Followers: 3)
Chemistry & Industry     Hybrid Journal   (Followers: 2)
Chemistry Central Journal     Open Access   (Followers: 5)
Chemistry of Materials     Full-text available via subscription   (Followers: 135)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 6)
ChemSusChem     Hybrid Journal   (Followers: 8)
Chinese Chemical Letters     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemical Engineering     Full-text available via subscription   (Followers: 3)
Chinese Journal of Chemical Physics     Hybrid Journal   (Followers: 1)
Coke and Chemistry     Hybrid Journal  
Coloration Technology     Hybrid Journal   (Followers: 1)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 8)
Computer Aided Chemical Engineering     Full-text available via subscription   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 7)
CORROSION     Full-text available via subscription   (Followers: 3)
Corrosion Engineering, Science and Technology     Hybrid Journal   (Followers: 22)
Corrosion Reviews     Hybrid Journal   (Followers: 4)
Crystal Research and Technology     Hybrid Journal   (Followers: 2)
Current Opinion in Chemical Engineering     Open Access   (Followers: 3)
Education for Chemical Engineers     Hybrid Journal   (Followers: 4)
Ekologia : The Journal of Institute of Landscape Ecology of Slovak Academy of Sciences     Open Access  
Eksergi     Open Access  
Emerging Trends in Chemical Engineering     Full-text available via subscription  
European Polymer Journal     Hybrid Journal   (Followers: 41)
Fibers and Polymers     Full-text available via subscription   (Followers: 3)
Fluorescent Materials     Open Access  
Focusing on Modern Food Industry     Open Access   (Followers: 3)
Frontiers of Chemical Science and Engineering     Hybrid Journal   (Followers: 1)
Gels     Open Access  
Geochemistry International     Hybrid Journal  
Handbook of Powder Technology     Full-text available via subscription   (Followers: 3)
Heat Exchangers     Open Access   (Followers: 1)
High Performance Polymers     Hybrid Journal  
Indian Chemical Engineer     Hybrid Journal   (Followers: 3)
Indian Journal of Chemical Technology (IJCT)     Open Access   (Followers: 12)
Industrial & Engineering Chemistry     Full-text available via subscription   (Followers: 9)
Industrial & Engineering Chemistry Research     Full-text available via subscription   (Followers: 20)
Industrial Chemistry Library     Full-text available via subscription   (Followers: 4)
Info Chimie Magazine     Full-text available via subscription   (Followers: 2)
International Journal of Chemical and Petroleum Sciences     Open Access   (Followers: 2)
International Journal of Chemical Engineering     Open Access   (Followers: 7)
International Journal of Chemical Reactor Engineering     Hybrid Journal   (Followers: 3)
International Journal of Chemical Technology     Open Access   (Followers: 4)
International Journal of Chemoinformatics and Chemical Engineering     Full-text available via subscription   (Followers: 2)
International Journal of Food Science     Open Access   (Followers: 3)
International Journal of Industrial Chemistry     Open Access  
International Journal of Polymeric Materials     Hybrid Journal   (Followers: 3)
International Journal of Science and Engineering     Open Access   (Followers: 7)
International Journal of Waste Resources     Open Access   (Followers: 5)
Journal of Chemical Engineering & Process Technology     Open Access   (Followers: 3)
Journal of Applied Crystallography     Hybrid Journal   (Followers: 4)
Journal of Applied Electrochemistry     Hybrid Journal   (Followers: 13)
Journal of Applied Polymer Science     Hybrid Journal   (Followers: 124)
Journal of Biomaterials Science, Polymer Edition     Hybrid Journal   (Followers: 8)

        1 2     

Journal Cover   Chemical Engineering Science
  [SJR: 1.178]   [H-I: 114]   [13 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0009-2509
   Published by Elsevier Homepage  [2812 journals]
  • Hydrate growth at the interface between water and pure or mixed CO2/CH4
           gases: Influence of pressure, temperature, gas composition and
           water-soluble surfactants
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Delphine Daniel-David , Fabrice Guerton , Christophe Dicharry , Jean-Philippe Torré , Daniel Broseta
      The morphology and growth of gas hydrate at the interface between an aqueous solution and gaseous mixtures of CO2 and CH4 are observed by means of a simple experimental procedure, in which hydrate formation is triggered at the top of a sessile water drop by contact with another piece of gas hydrate and the ensuing hydrate growth is video-monitored. The aqueous solution is either pure water or a solution of a nonionic or anionic surfactant at low concentration (in the 100–1000ppmw range). In agreement with previously published data, hydrates formed from pure water and aqueous solutions of non-ionic surfactant grow rapidly as a low-permeable polycrystalline crust along the water/gas interface, which then inhibits further growth in a direction perpendicular to the interface. Lateral growth rates increase strongly with subcooling and CO2 content in the gas mixture. Similar lateral growth rates, but varying morphologies, are observed with the non-ionic surfactants tested. In contrast, the two anionic surfactants tested, sodium dodecyl sulfate (SDS) and dioctyl sodium sulfosuccinate (AOT), promote in the presence of CH4 (but not in the presence of CO2) a rapid and full conversion of the water drop into hydrate through a ‘capillary-driven’ growth process. Insights are given into this process, which is observed with AOT for an unprecedented low concentration of 100ppmw.


      PubDate: 2015-05-26T10:06:52Z
       
  • Optimizing spatial pore-size and porosity distributions of adsorbents for
           enhanced adsorption and desorption performance
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Guanghua Ye , Xuezhi Duan , Kake Zhu , Xinggui Zhou , Marc-Olivier Coppens , Weikang Yuan
      This paper shows that a uniform spatial distribution in meso/macroporosity of adsorbents maximizes their adsorption and desorption performance. It highlights the importance of optimizing porosity and pore diameter, not only at the nanoscale but also at larger length scales. The effects of spatial pore size and porosity distributions on mass transfer in adsorbents are studied by using a continuum approach. These effects are evaluated by comparing the adsorption/desorption performance of adsorbents subjected to a square wave concentration perturbation with a wide range of cycle period (10–100,000s) for the adsorption of n-pentane on 5A zeolite adsorbents. The uniformly distributed pore size and porosity is the preferred structure, which is confirmed by using four empirical tortuosity–porosity relations. Further optimization of the uniform structure shows that its optimal average porosity is in the range of 0.4–0.6 when the perturbation cycle period is between 100s and 2000s and the volume-averaged pore diameter is between 10nm and 150nm. The relationships between optimal average porosity, cycle period and volume-averaged pore diameter are determined and explained. These results should serve to guide the synthesis of adsorbents.


      PubDate: 2015-05-26T10:06:52Z
       
  • Editorial Board
    • Abstract: Publication date: 28 July 2015
      Source:Chemical Engineering Science, Volume 131




      PubDate: 2015-05-26T10:06:52Z
       
  • Table of Contents
    • Abstract: Publication date: 28 July 2015
      Source:Chemical Engineering Science, Volume 131




      PubDate: 2015-05-26T10:06:52Z
       
  • Porous media Eulerian computational fluid dynamics (CFD) model of amine
           absorber with structured-packing for CO2 removal
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Dung A. Pham , Young-Il Lim , Hyunwoo Jee , Euisub Ahn , Yongwon Jung
      A gas–liquid Eulerian porous media computational fluid dynamics (CFD) model was developed for an absorber to remove CO2 from natural gas by mono-ethanol-amine (MEA). The three dimensional geometry of the amine absorber packed with nine elements of Mellapak 500.X (M500X) was constructed for the CFD domain. The momentum conservation equation included the porous resistance, gas–liquid momentum exchange and liquid dispersion to replace the structured-packing by the porous media model. The mass conservation equation involved the mass transfer of CO2 gas into the MEA solution and one chemical reaction. The mesh independent test was performed on coarse, medium and fine meshes and the medium mesh (37,400 cells) was selected for further investigation. Parameters of the CFD model were adjusted to fit experimental data (wet pressure drop, liquid holdup, and CO2 mole fraction along the column height) measured in a CO2-MEA system on M500X. This study demonstrated that the porous media CFD model can treat both hydrodynamics and CO2 removal in the amine absorber with structured-packing.


      PubDate: 2015-05-26T10:06:52Z
       
  • A local composition model for the prediction of mutual diffusion
           
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Qingyu Zhu , Geoff D. Moggridge , Carmine D’Agostino
      In a recent publication (Moggridge, 2012a. Chem. Eng. Sci. 71, 226–238), a simple equation was shown to accurately predict the mutual diffusion coefficients for a wide range of non-ideal binary mixtures from the tracer diffusion coefficients and thermodynamic correction factor, on the physical basis that the dynamic concentration fluctuations in the liquid mixture result in a reduction of the mean thermodynamic correction factor relative to the hypothetical case in which such fluctuations do not occur. The analysis was extended to cases where strong molecular association was hypothesised to occur in the form of dimerization of a polar species in mixtures with a non-polar one. This required modification of the average molecular mobility in the form of doubling the tracer diffusivity of the dimerized species (Moggridge, 2012b. Chem. Eng. Sci. 76, 199–205). Predictions were found to show good accuracy for the mixtures investigated. One of the difficulties with this approach is that it is an a posteriori correction: there is no a priori way of knowing whether strong cluster formation influences the observed molecular mobility, or what the appropriate size of the cluster is. In this work, a modification is made to the average molecular mobility in the original equation by replacing the bulk mole fraction with local mole fraction calculated using the NRTL (non-random two liquid) model, to take account of strong molecular association that results in highly correlated movement during diffusion. The new equation enables an accurate description of mutual diffusion coefficients in mixtures of one strongly self-associating species and one non-polar species, as well as in non-ideal, non-associating mixtures. This result is significant because in this way there is no need of any prior knowledge on the degree of molecular association in the mixture for the prediction of mutual diffusion coefficients from tracer diffusivities.


      PubDate: 2015-05-26T10:06:52Z
       
  • Systematic study of the effect of electrolyte composition on interfacial
           tensions between surfactant solutions and crude oils
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Thomas Tichelkamp , Erlend Teigen , Meysam Nourani , Gisle Øye
      Dynamic and equilibrium interfacial tensions (IFT) were measured between four crude oils and aqueous low salinity solutions of the anionic surfactant AOT with different molar ratios between calcium and sodium ions. The ion strength of the electrolyte was kept constant at 20mmol/L for all experiments. Slight changes of the calcium/sodium ratio altered the equilibrium oil/water IFT by more than one order of magnitude in the presence of surfactant. Experiments, in which either AOT was excluded or crude oil was replaced by pure hydrocarbons, were conducted in order to determine the relative impact of surfactant–electrolyte and crude oil–electrolyte interactions. In the presence of calcium, AOT dominated the interfacial properties. In sodium brine synergistic effects of AOT and surface active oil components on IFT were observed.


      PubDate: 2015-05-26T10:06:52Z
       
  • Zonal description and quantitative methodology of air–water
           distribution in comb-like microchannels
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Weihua Zhang , Feng Xin , Dongyue Peng , Lexiang Zhang
      The goal of this study was to determine feasible numbering-up laws to model the gas–liquid distribution in multiple microchannels. Comb-like microchannels were constructed by closely arranging eight capillaries of 0.5-mm inner diameter. The air–water flow in the parallel microchannels was recorded by a high speed CCD camera. After collecting and analyzing a very large number of images, the flow patterns were classified into two zones, zone I and zone II, which were the bubble flow and phase splitting zones, respectively. A model was established to describe the mean sizes and velocities of bubbles and liquid slugs in the two zones at different inlet flow rates of air and water, as well as to distinguish the two-zone operating limits by determining inlet flow rate intervals of the fluids. The calculated results agreed well with the experimental data. Therefore, the model showed a potential application to numbering up comb-like microchannels.


      PubDate: 2015-05-26T10:06:52Z
       
  • Experimental study of the effects of geometrical parameters, Reynolds
           number, and equivalence ratio on methane–oxygen premixed flame
           dynamics in non-adiabatic cylinderical meso-scale reactors with the
           backward facing step
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Mohammadreza Baigmohammadi , Sadegh Tabejamaat , Yasaman Farsiani
      In this study, we experimentally investigated the effects of geometrical parameters (such as the reactor length (L) and the inner diameter (D R)), the step height ( r in − r R ) , the Reynolds number (Re), and the equivalence ratio (φ)) of the inlet mixture on the behavior of the rich fuel methane–oxygen flames in non-adiabatic cylindrical meso-scale reactors with the backward facing step. During the experiments, seven different flame regimes were observed. These flame regimes were the blow-out, marginal, stationary (stable), RERI, stationary (stable)-flashback, RERI-flashback, and flashback, respectively. Also, the results showed that the length and diameter of reactors could strongly affect flame dynamics, especially the borders among the observed flame regimes in the meso-scale reactors. As a result, it was demonstrated that the reactor length and diameter obviously influenced the traveling speed and frequency of RERI flame regime. Also, it was shown that decreasing the step height from 1.4mm to 0.4mm suppressed RERI flame regime in the meso-scale reactors. Moreover, in the certain ranges of the equivalence ratio, increasing the Reynolds number decreased the flame presence range in the meso-scale reactors. Finally, it was concluded that RERI flame regime is a prevalent operational regime for applications in which an almost uniform temperature pattern on the outer surface of lengthy meso-scale reactors is required. However, it was shown that this privilege was not valid as compared to the temperature distribution patterns caused by the stationary flame regimes in the small length reactors.


      PubDate: 2015-05-26T10:06:52Z
       
  • Reacting porous solids with phase segregation
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Tommaso Melchiori , Fausto Gallucci , Martin Van Sint Annaland , Paolo Canu
      In this work, a detailed single particle model was developed to describe the reaction of porous solids consisting of different solid species, with an initial composition that can be non-uniformly distributed along its radius, and multiple reactions. The continuous particle model is used to describe the rate of reduction of iron–titanium oxide particles for Chemical Looping Combustion processes, considering a two-step reaction mechanism involving two solid reagents: hematite and pseudobrookite. The experimentally observed non-uniform initial distribution of solid species, as a consequence of the solids activation procedure, was accounted for by assuming an initial core–shell structure with a diffused interface with different compositions of the two areas of the pellets. A detailed sensitivity analysis was carried out assuming different kinetics and initial concentration profiles of the different solid species involved. The results confirm that the initial distribution of hematite and pseudobrookite has a major influence on the predicted particle conversion rate. A comparison was carried out with experimental data obtained by thermogravimetric analysis for the reduction of small spherical ilmenite particles (200µm) with CO and H2 at 600–800°C and at atmospheric pressure. The study proves that the model can explain features of the experimental results that do not fit any shrinking core model.


      PubDate: 2015-05-26T10:06:52Z
       
  • Experimental study of the heat transfer coefficient deterioration during
           Density Wave Oscillations
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Mikkel Sørum , Carlos A. Dorao
      The effect of the Density Wave Oscillations (DWO) on the heat transfer is studied experimentally. A horizontal test section of 5mm I.D. with R134a as working fluid was used for the experiments. The time averaged boiling heat transfer was found to be different under DWO conditions than under steady-state flow. Four different cases were studied considering different inlet pressure, temperature and mass flow rate. It was observed that the occurrence of the DWO can result in a premature dry-out and that the impact of the DWO on the heat transfer depends on the particular conditions. However for the studied cases the impact on the heat transfer was not severe.


      PubDate: 2015-05-26T10:06:52Z
       
  • Influence of cationic and non-ionic surfactants on the kinetics of mixed
           hydrogen/tetrahydrofuran hydrates
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Hari Prakash Veluswamy , Wei Jun Ang , Dan Zhao , Praveen Linga
      In this study, the kinetics of mixed hydrogen/tetrahydrofuran (THF) hydrate formation in presence of cationic dodecyl trimethylammonium chloride (DTAC) surfactant and non-ionic Tween-20 (Polysorbate 20) surfactant was evaluated. Stoichiometric concentration of 5.6mol% THF solution with varying surfactant concentrations from 0.01wt% to 1wt% were experimented and their effect on the mixed hydrogen/THF hydrate formation was studied. Marginal improvement in the mixed hydrogen/THF hydrate formation rates were observed for both the chosen surfactants with maximum of about 20% increase using 0.5wt% DTAC and 0.1wt% Tween-20. Decomposition kinetics of mixed hydrogen/THF hydrates using thermal stimulation (ΔT=20K) with and without stirring showed that stirring improved the decomposition kinetics with t 90 of 22.2(±0.8)min in comparison to t 90 of 29.1(±0.6)min for the experiments conducted without stirring. The presence of surfactant did not significantly affect the decomposition kinetics for experiments conducted both with and without stirring. Methane/THF mixed hydrate formation under similar experimental conditions studied show that the presence of 0.5wt% DTAC surfactant resulted in reduction of hydrate formation rates by approximately 20%. The effect of surfactant in presence of THF characteristically differs depending upon the guest gas and the system under investigation.
      Graphical abstract image

      PubDate: 2015-05-26T10:06:52Z
       
  • On the negative activation energy for limestone calcination at high
           temperatures nearby equilibrium
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Jose Manuel Valverde
      The study of limestone calcination under high CO2 pressure and high temperature has gained an extraordinary practical importance due to the recently emerged Ca-looping technology for post-combustion CO2 capture, which uses natural limestone (CaCO3) as precursor of the CO2 solid sorbent (CaO). A critical issue of this promising process is the necessity of producing CaO by calcination of limestone under high CO2 partial pressure. Experimental measurements on the kinetics of limestone calcination usually show that the rate of the endothermic calcination reaction is increased with temperature according to an Arrhenius law with an activation energy similar to the reaction enthalpy change. In situ microscopic observations have demonstrated that the reaction involves a crystallographic structural transformation of CaO. Calcination is started by chemical decomposition leading to the development of metastable CaO⁎ nanocrystals after which CO2 is desorbed while stable CaO cubic crystals grow. In calcination environments with low CO2 partial pressure P (as compared to the equilibrium pressure: P / P eq ≪ 1 ), desorption of CO2 and the exothermic structural transformation of CaO⁎ to its stable CaO form occur extremely fast and do not play a role on the reaction kinetics, which is just determined by chemical decomposition. However, at high values of P / P eq the reaction rate may be significantly influenced by the structural transformation above a critical temperature. As a main consequence, the reaction mechanism proposed in the present paper shows that, above a critical temperature, limestone calcination is characterized by a negative activation energy in agreement with the experimental results shown.


      PubDate: 2015-05-26T10:06:52Z
       
  • q-Quadratic mixing rule for cubic equations of state
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Leonardo S. Souza , Ernesto P. Borges , Fernando L.P. Pessoa
      We introduce a new nonquadratic mixing rule that models correlations between species by means of the q-product of mole fractions, instead of the ordinary product. The use of the q-product is a procedure adopted within the nonextensive statistical mechanics formalism in the generalization of the central limit theorem for strongly correlated systems. The proposal is a generalization of the ordinary van der Waals quadratic law that is recovered when the so-called nonquadraticity binary parameter takes the limit q ij → 1 . The proposed q-mixing rule has been tested by evaluating vapor–liquid equilibrium at different temperatures for systems containing alcohol, hydrocarbons and CO2, species that yield departures from ideality. Two distinct approaches, the Akaike Information Criterion and the F-test, were used to compare the q-mixing rule and the van der Waals mixing rule.


      PubDate: 2015-05-26T10:06:52Z
       
  • Numerical simulation of mixing and reaction of Jatropha curcas oil and
           ethanol for synthesis of biodiesel in micromixers
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Harrson S. Santana , João L. Silva Jr , Osvaldir P. Taranto
      Great advances have been recently made in the area of miniaturization of systems. One of the most important aspects of these microdevices is the mixing of the reacting species, which will determine its conversion to the desired product. These microdevices have been successfully applied in the synthesis of biodiesel, mainly due to increased conversion of reactants in a short residence time. Oils derived from non-edible oil seeds are promising feedstock sources for biodiesel, especially Jatropha species. As a result, this paper numerically studied the mixing and reaction of Jatropha curcas oil and ethanol in micromixers for the production of biodiesel. Three types of micromixers were studied: T-micromixer, Cross-micromixer and Double-T-micromixer. The efficiency of each type was analyzed using a mixing index, which is calculated using the variation of mass fraction, and the conversion of oil. The mixing of the fluid was analyzed with different Reynolds numbers and the conversion of oil was analyzed for different Reynolds numbers and residence times. All showed excellent degree of mixture for low Reynolds numbers, with the Cross-micromixer showing the highest degree of mixing. By increasing the Reynolds number the mixing in the T-micromixer was increased, reduced in the Double-T-micromixer and did not affect the mixture in the Cross-micromixer. It was observed that the conversion obtained in all micromixers is practically constant and is not affected by the variation of Reynolds number studied (10–100). The Cross-micromixer presented the best reaction yield. An increment in residence time increased the conversion of oil. This work numerically demonstrated the possibility of using J. curcas as a feedstock for synthesis of biodiesel in microchannels.
      Graphical abstract image

      PubDate: 2015-05-26T10:06:52Z
       
  • Maxwell–Stefan modeling of mass transfer in solvent impregnated
           resins
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): J. Bokhove , P.J.A.M Kerkhof , B. Schuur , A.B. de Haan
      Solvent impregnated resins are promising for the removal of polar organic compounds from aqueous streams, but have low mass-transfer rates. A thorough understanding of the phenomena occurring inside the pores of the solvent impregnated resin is therefore required. In this study a mathematical model was developed to describe the simultaneous diffusion and reaction. The diffusion was described using the Maxwell–Stefan approach towards multi-component diffusion and included the volume-expansion of the organic phase. The model was validated using experimental data from the literature on the extraction of phenol by Cyanex923 impregnated in macro-porous polypropylene. The model described the experimental data as function of temperature and initial concentration accurately with an R 2>0.96 and a regressed reaction rate constant with a confidence interval of ±6%. Analysis of the model results revealed that multi-component effects as described by the Maxwell–Stefan model were of limited importance whereas the volume expansion was essential to accurately describe the experimental data.


      PubDate: 2015-05-26T10:06:52Z
       
  • Dynamics of bubble breakup with partly obstruction in a microfluidic
           T-junction
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Xiaoda Wang , Chunying Zhu , Yining Wu , Taotao Fu , Youguang Ma
      The bubble breakup with partly obstruction in a microfluidic T-junction was investigated experimentally in this paper. It was demonstrated that the breakup process could be divided into two stages: squeezing stage and pinch-off stage, according to the evolution of the minimum width of the bubble neck w m. During the squeezing stage, the variation of 1−w m/w c with time t could be scaled by a power law. In the pinch-off stage, the minimum width of the bubble neck w m could also be correlated into a power law function with the remaining time (T c−t). A tunnel, which characterized the bubble breakup with partly obstruction, appeared between the bubble tip and the microchannel wall in the squeezing stage, and exhibited little effect on the evolution of the bubble neck. However, the evolution of the bubble tip was obviously different before and after tunnel appearance. By means of the analysis on the dynamics of the bubble tip, some important parameters such as the final bubble length and the leakage volume were studied and discussed.
      Graphical abstract image

      PubDate: 2015-05-26T10:06:52Z
       
  • Effect of channel gap distance on the flame blow-off limit in mesoscale
           channels with cavities for premixed CH4/air flames
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Jianlong Wan , Aiwu Fan
      The development of simple and effective flame stabilization methods is crucial for micro- and mesoscale combustors. In the present paper, flame stability in a mesoscale channel with cavities was experimentally investigated, and the effect of the channel gap distance on the flame blow-off limit was examined. Experimental results demonstrate that the stable operational range of the combustor is extended in the presence of cavities, which act as a flame holder. Meanwhile, the flame blow-off limit increases as the channel gap distance is increased. Numerical simulation was conducted to facilitate analysis of the underlying mechanisms responsible for the differences in flame blow-off limits. Analyses reveal that effects of heat loss and heat recirculation are the two dominant factors that lead to different blow-off limits. First, the heat recirculation effect is more prominent for a larger channel gap distance, which exhibits much more intense initiation reactions. In addition, with the decrease of the channel gap distance, the heat loss rate from the flame root becomes larger, and the flame root is liable to be thermally quenched by the cavity walls. In conclusion, the fresh mixture is better preheated by the recirculated heat, and the heat loss rate from the flame root is also lower when the channel gap distance is larger. Hence, a larger flame blow-off limit can be expected for a channel with a wider gap.


      PubDate: 2015-05-26T10:06:52Z
       
  • Free-surface dynamics of small pores
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Jiakai Lu , Carlos M. Corvalan
      When the size of a pore nucleated in a fluid sheet is sufficiently small, the pore will contract and close driven by its large radial curvature. The dynamics of small contracting pores are relevant to a number of natural systems and practical applications, from fission pores in cell membranes to the fabrication of nanopores in sensors for DNA sequencing. Here, we report high-fidelity numerical simulations that provide detailed insight into the mechanisms of pore contraction and collapse in fluid sheets of low viscosity. Results uncover a scaling law that predicts the radius of a closing pore as a function of the time to collapse without free parameters. Simulations also show that contracting pores do not always proceed to collapse. Instead, some contracting pores reverse the direction of motion and expand.


      PubDate: 2015-05-26T10:06:52Z
       
  • Random walk simulation of miscible flow through heterogeneous 2D porous
           media considering dispersion tensor
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Amir Fayazi , Mohammad Hossein Ghazanfari
      Most of numerical approaches describing the behavior of miscible displacement in porous media through the solution of advection–dispersion equation suffer from numerical dispersion. Random Walk (RW) method is a good candidate to overcome this problem especially in heterogeneous media. In addition, how treating dispersion coefficient as a tensor might affect the accuracy of RW simulation results is not well understood. Here, a RW model was developed and used for simulating miscible displacement experiments performed on heterogeneous micromodels including single fracture/flow barrier. Dispersion coefficient was treated as a tensor and a hybrid scheme was used for velocity interpolation. The transient concentration and production data were used for estimation of the diffusion coefficient, longitudinal and transversal dispersivity by fitting the model results to the experimental data. Well match observed between model results and experimental data indicates that RW is an accurate method for simulating miscible displacements by capturing the irregularity of the saturation profiles.


      PubDate: 2015-05-26T10:06:52Z
       
  • Measurement of oil entrainment rates and drop size spectra from
           coalescence filter media
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): S. Wurster , D. Kampa , J. Meyer , T. Müller , B.J. Mullins , G. Kasper
      Liquid entrainment from coalescence filter media—i.e. flow induced “blow-off” of previously deposited oil—in the form of droplets is poorly understood, for one because the generated spectrum is very wide and difficult to characterize with temporal and size resolution, especially for very large drops which carry most of the mass. Such filters operate at much lower flow rates than classical demisters, often in vertical orientation, with much finer geometries, and gravity plays no direct role for entrainment. We present a novel combination of four measurement techniques used to capture the entrained oil drop spectrum from filters during operation in the size range of 0.01–2400µm. The diameter range below 10μm combines two established real-time methods including an electrical mobility particle spectrometer (EMPS; <1μm) and an optical particle counter (OPC; 0.3 to 10μm). The diameter range above 170μm is covered by a newly developed “large drop detection system” (LDDS) based on single particle light scattering. OPC and LDDS continuously count and classify all drops originating from the entire filter coupon with a time resolution of 1min. The EMPS was operated intermittently, following brief switches from aerosol to clear air flow. Drops in the size range between OPC and LDDS were collected and sized by an off-line method. This measuring system was applied to two representative types of glass microfiber media operated with oil mist generated from compressor oil, in order to characterize time resolved drop formation rates and spectra in the range of nanometers to millimeters. Wettable and non-wettable filter media were found to show similar entrainment characteristics, each with multi-modal drop spectra having two pronounced peaks in the ranges of 1–2μm and 200–300μm, respectively. During steady-state operation both modes were generated quasi-continually, the large drops at the rate of a few drops per hour and cm2 of filter surface, the micron size drops 103–104 times more frequently. Available indirect evidence suggests the same underlying entrainment mechanism for both types of fibrous media, namely the break-up of air bubbles formed periodically on the oil that drains on the downstream filter face. Direct detachment (blow-off) of large drops is unlikely at the prevailing operating conditions.


      PubDate: 2015-05-26T10:06:52Z
       
  • Predicting optimal temperature profiles in single-stage fixed-bed reactors
           for CO2-methanation
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Lars Kiewidt , Jorg Thöming
      The catalytic conversion of carbon dioxide into methane, known as Sabatier process, is a promising option for chemical storage of excess renewable energy and greenhouse gas emission control. Typically externally cooled fixed-bed reactors (FBR) using supported nickel or ruthenium catalyst are applied. The Sabatier process, however, is strongly exothermic and leads to substantial hot spots within the reactor at stoichiometric feed ratios. Although high temperatures increase the reaction rate in general, they thermodynamically limit the achievable methane-yield in the Sabatier process. Here, we present an easy-to-use method based on a Semenov number optimization (SNO) to compute optimal axial temperature profiles in single-stage fixed-bed reactors that account for kinetic and thermodynamic limitations simultaneously, and thus result in maximized yield for a fixed reactor length. In a case study on CO2-methanation, these temperature profiles result in a twofold improvement of the methane-yield compared to isothermal and adiabatic operation, and thus demonstrate the high potential of thermal optimization that lies in the Sabatier process. The SNO-method provides a valuable tool to compute optimal temperature profiles, and allows intuitive insight into the key parameters for thermal process intensification. Further, it can readily be transferred to other processes that suffer from the dilemma between kinetic and thermodynamic limitations. Our findings illustrate the attractiveness of the SNO-method to compute optimal temperature profiles in fixed-bed reactors, and the need for catalyst supports with enhanced and tailorable heat transport properties.
      Graphical abstract image Highlights

      PubDate: 2015-05-26T10:06:52Z
       
  • Hydrodynamic modelling of complex fixed bed geometries in simulated moving
           bed adsorption processes
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): L. Fangueiro Gomes , F. Augier , D. Leinekugel-le-Cocq , I. Vinkovic , S. Simoëns
      Hydrodynamics inside industrial simulated moving bed (SMB) adsorption columns can be complex due to the presence of internal distribution devices. They have to be taken into account in SMB numerical models to scale-up processes. In the present work, CFD is used as an intermediate step to develop a 1D model simple enough to be used for cyclic SMB simulations while being able to represent realistic hydrodynamics. First, a mock-up representative of an industrial SMB is used to perform residence time distribution (RTD) experiments and to provide validation data. Experiments are well predicted by a CFD model including porous media and turbulent zones, allowing to consider CFD simulations as references to fit simpler models. The moments of internal age distribution are characterized following the calculation method developed by Liu and Tilton, 2010. AIChE J. 56(10), 2561–2572, which allows to estimate the degree of mixing (Liu, 2012. Chem. Eng. Sci. 69(1), 382–393) inside adsorption beds. A major result is that RTD and degree of mixing inside adsorption beds are well described by a 1D multi-exit model, unlike classical dispersed plug flow models (Ruthven and Ching, 1989) that were generally used to simulate SMB processes. Additionally, a numerical method was developed which is able to reproduce the RTD with steady state simulations.


      PubDate: 2015-05-26T10:06:52Z
       
  • Mass transfer and shear rate on a wall normal to an impinging circular jet
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Magdalena Kristiawan , Kodjovi Sodjavi , Brice Montagné , Amina Meslem , Vaclav Sobolik
      The electrodiffusion technique and the time-resolved tomographic PIV were used in impinging jet issued from a convergent conical nozzle at a Reynolds number of 2450 based on the nozzle diameter d and the jet exit velocity. The relative distance from the nozzle to the impinging wall was equal to h/d=2. The experimentally gained velocity fields provides information on the organization of coherent flow structures, which play a role in the wall shear rate and the mass transfer phenomenon at the impinged wall. Instantaneous wall shear rate and local mass transfer were measured at an impinging wall using platinum electrodes with a diameter of 0.5mm flush mounted into a platinum disc electrode with a diameter of 49.5mm. The small electrodes were used alternately for the measurement of wall shear rate and mass transfer. The proposed correction factor on the inertia of the concentration boundary layer, which is the ratio of the corrected fluctuations of wall shear rate to their primary values, along with the analysis of the signals history, provide valuable information on the state of the hydrodynamic boundary layer. The mean wall shear rate and local mass transfer exhibit their maximum values at the normalised radial positions r/d=0.6–0.7. There are the interactions of the primary Kelvin–Helmholtz (K–H) vortices with smaller structures issued from the breaking-down of these vortices, both rotating in the same direction. Counter-rotating secondary vortices form between the wall and primary K–H vortices at a radial distance about r/d=1.5. They are present in a wide region (r/d~1.5 to 2.5); around r/d=1.5 they are very close to the wall leading to a clear periodicity of wall shear rate, and at r/d=2.5 they are farther above the wall since no periodicity of the wall shear rate was observed. The local mass transfer rates were integrated and compared with the global mass transfer measured by a platinum disc electrode.


      PubDate: 2015-05-26T10:06:52Z
       
  • Investigation of a swirling flow nozzle for a fluidised bed gas
           distributor
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Samson M. Aworinde , Daniel J. Holland , John F. Davidson
      This paper relates to a multi-orifice distributor for a gas-fluidised bed, using many upward-facing nozzles, equally spaced in a horizontal plate. Each orifice contained a removable helical coil, which made the gas swirl as it entered the bed. For a single orifice in such a distributor, ultra-fast magnetic resonance imaging (MRI) and pressure measurements were applied to study: (i) the formation of jets and bubbles and (ii) the orifice pressure drop. Results from MRI show that the swirling flow induced by the helix significantly improves the fluidisation quality compared to a plain nozzle without spiral. The helix gives rise to secondary flow which increases pressure drop across the nozzle, the measured values of which are predicted satisfactorily by using a friction factor correlation for helical coils.
      Graphical abstract image

      PubDate: 2015-05-26T10:06:52Z
       
  • Nonlinear Frequency Response measurements of gas adsorption equilibrium
           and kinetics: New apparatus and experimental verification
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Danica Brzić , Menka Petkovska
      A new apparatus for experimental validation of the Nonlinear Frequency Response (NFR) method for investigation of gas adsorption is presented. The apparatus has been designed as a batch adsorber with sinusoidal modulation of the volume, with an amplitude that can be varied. Fast and accurate measurements of pressure, gas temperature and particle temperature responses are employed. The measurement routine and data analysis are demonstrated by CO2 adsorption on zeolite 5A particles of two different diameters. The responses for input amplitudes of 3% and 7% of the volume change are measured. The concept of blank FRFs is introduced as a new way to incorporate the results of blank experiments for elimination of spurious effects. The first- and second-order FRFs which relate the adsorbed quantity to the pressure (F 1(ω) and F 2(ω,ω)) are calculated based on the measured pressure responses. The first-order FRF which relates the particle temperature to the pressure (H 1(ω)) is calculated from the particle temperature responses. The characteristics of F 1(ω), F 2(ω,ω) and H 1(ω) for spherical beads of 1.7mm agree with the corresponding theoretical ones for nonisothermal macropore diffusion model. The equilibrium and kinetic parameters are estimated from these functions. The results of this study confirm the applicability of NFR method for characterization of gas adsorption and show significance of the extension of analysis to the nonlinear range.


      PubDate: 2015-05-26T10:06:52Z
       
  • The dynamic mass transfer of surfactants upon droplet formation in coaxial
           microfluidic devices
    • Abstract: Publication date: 18 August 2015
      Source:Chemical Engineering Science, Volume 132
      Author(s): Yang Chen , Guo-Tao Liu , Jian-Hong Xu , Guang-Sheng Luo
      In this work, the dynamic adsorption of surfactants is used to evaluate the mass transfer coefficient during droplet formation. As surfactants exist in only one phase and at the interface, the resistance of mass transfer inside and outside the droplet can be decoupled. By exchanging the continuous phase and dispersed phase (N-hexane/water-Tween 80), the mass transfer coefficients inside and outside the droplet were evaluated. A semi-empirical equation with modified parameters was developed to incorporate the effects of convection and the experimental conditions on the mass transfer coefficient during droplet formation in micro-channels. The results presented in this work provide a more in-depth understanding of the dynamic mass transfer of surfactants inside and outside the droplet during the formation of a droplet in microfluidic devices.
      Graphical abstract image

      PubDate: 2015-05-26T10:06:52Z
       
  • Hydrodynamic study of a Two-Section Two-Zone Fluidized Bed Reactor with an
           immersed tube bank via PIV/DIA
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): I. Julián , F. Gallucci , M. van Sint Annaland , J. Herguido , M. Menéndez
      The hydrodynamic behaviour of a pseudo-2D Two-Section Two-Zone Fluidized Bed Reactor (TS-TZFBR) with an immersed tube bundle in its lower zone has been studied using non-invasive Particle Image Velocimetry (PIV) and Digital Image Analysis (DIA). Coupled porosity distribution maps from DIA post-processing and solids velocity vector fields from PIV analysis allowed the reconstruction of the transient and time-averaged solid fluxes along the bed. Six different tube bank configurations at several different superficial gas velocities have been tested to evaluate the hydrodynamic behaviour within the lower zone of the TS-TZFBR. The solids axial mixing along the vertical bed position has been quantified for this novel reactor configuration. Besides, the effect of the internals on the gas-solid mass transfer has been estimated by means of bubble size. A five-staggered tube bundle configuration was able to diminish the average bubble size by 30% within the lower bed zone at usual TS-TZFBR gas flow rates, u gas/u mf=3.0, without increasing the solids circulation time dramatically.
      Graphical abstract image

      PubDate: 2015-05-26T10:06:52Z
       
  • Kinetic and reaction pathway of upgrading asphaltene in supercritical
           water
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Ning Li , Bo Yan , Xian-Ming Xiao
      Experiments of upgrading asphaltene in Supercritical Water (SCW) were conducted in autoclaves with sealed gold tube reactors to elucidate the reaction pathway and reaction kinetics. The experiments were performed at temperature of 400–450°C, pressure of 30MPa and residence time ranging from 0 to 120min. The products obtained from the upgrading asphaltene in SCW included gas, maltene and coke. Kinetic analysis showed that upgrading asphaltene in SCW obeyed a first-order kinetic with apparent activation energy of 51.11kJ/mol. Three possible 4-lump kinetic models were proposed to discuss the detailed reaction pathway of upgrading asphaltene in SCW. The first-order kinetic equations were used to evaluate the reliability of each model from the aspect of correlation coefficient (R 2). The results showed that Model 2, considering the parallel reaction of asphaltenes transformation to gas, maltene and coke, the consecutive reaction from maltene to gas and coke, the secondary reaction of coke to gas, was illustrated as the optimal reaction pathway model for upgrading asphaltene in SCW.
      Graphical abstract image

      PubDate: 2015-05-26T10:06:52Z
       
  • Image analysis of X-ray tomograms of sludge during convective drying in a
           pilot-scale fixed bed
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Jie Li , Erwan Plougonven , Laurent Fraikin , Thierry Salmon , Dominique Toye , Angélique Léonard
      Shrinkage is an important phenomenon during sludge drying, as a significant reduction in volume occurs during the loss of moisture. As the structure changes, the drying area decreases and the drying rate reduces accordingly. X-ray tomography is used to explore the structure evolution that a sludge bed undergoes in a convective pilot-scale fixed bed dryer. A high energy (420kV), large-scale (max. 0.45m in diameter and max. 4m in height) X-ray tomograph with a spatial resolution of approximately 0.36mm was chosen. Two types of sludge samples collected in two wastewater treatment plants (Grosses Battes WWTP and Oupeye WWTP, Belgium) were chosen for this study. Continuous and intermittent drying experiments were both carried out to study the drying kinetics and structure evolutions (volume, shrinkage, void, exchange surface). After experiments, 2D cross-sections and 3D images were obtained, which provide a convenient way to obtain global and quantitative information on the evolution of the sludge bed structure during the entire drying process. The results show that the volume, shrinkage, void, and exchange surface all substantially change during the drying process. Moreover, the structures of the two sludges evolve quite differently during the drying process. Image analysis of the X-ray tomograms is used to gain insight on the transport phenomena that occur during the drying process.
      Graphical abstract image

      PubDate: 2015-05-26T10:06:52Z
       
  • Theoretical investigations of sp–sp2 hybridized capped graphyne
           nanotubes
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Jie Gong , Yunqing Tang , Haiying Yang , Ping Yang
      The aim of this paper is to demonstrate a new material of a capped graphyne nanotube with sp–sp2 hybridization. In order to prove the possible existence of this structure, frequency, binding energy and kinetic stability calculations are carried out by means of density functional theory (DFT) calculation and molecular dynamics (MD) confirmation. For the understanding of the geometric structure and electronic properties, C–C bond lengths of this structure are analyzed. The energy gap between the highest occupied molecular orbital (HOMO) state and the lowest unoccupied molecular orbital (LUMO) state is calculated, and electrostatic potential (ESP) derived charges and local electron density distributions of the capped graphyne nanotube are explored. In addition, the changing trend of energy gap with the increasing electric field is used to describe the field emission properties of the structure. Finally, we calculate work functions and ionization potentials under the different electric fields to estimate potential field emission properties directly.


      PubDate: 2015-05-26T10:06:52Z
       
  • Bubble coalescence: Effect of bubble approach velocity and liquid
           viscosity
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Sandra Orvalho , Marek C. Ruzicka , Giuseppe Olivieri , Antonio Marzocchella
      The goal of this study is to present new experimental data on the effect of the bubble approach velocity and liquid viscosity on pairwise bubble coalescence. Measurements were performed to investigate the dynamics of bubble coalescence under well-defined laboratory conditions. Air and pure aqueous solutions of alginate (no surfactants) were the phases. The bubbles were formed from two vertical capillaries, under constant flow conditions. The coalescence process was recorded with a fast video and then image analysed, to evaluate the bubble growth, bubble expansion rate, the first bubble touch, bubble contact time T, bubble coalescence efficiency E. Three control parameters were tested. The bubble size D on contact was set by the spacing between the capillaries (D=1 and 1.5mm). The bubble approach velocity V was controlled by the gas input (V=0.031–39mm/s). The liquid viscosity μ was adjusted by the alginate content (μ=1.2–10.3mPas). It was found that the bubble contact time T monotonously increases with the liquid viscosity, passing through three stages: initial rise (low μ, coalescence), then jump (intermediate μ, transient region), and finally forming a plateau (high μ, non-coalescence). In the coalescent regime, the bubble contact time monotonously decreases with the bubble approach velocity obeying a power law, which for a typical 1mm bubble reads: T∼V −0.85. The difference in the bubble size did not change the coalescence pattern qualitatively, but only quantitatively in a modest manner.
      Graphical abstract image

      PubDate: 2015-05-26T10:06:52Z
       
  • Mechanism and kinetics of titanium hydrolysis in concentrated titanyl
           sulfate solution based on infrared and Raman spectra
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Weijing Wang , Yahui Liu , Tianyan Xue , Jie Li , Desheng Chen , Tao Qi
      The titanium hydrolysis in the concentrated titanyl sulfate solution is essential to the TiO2 production by using the new NaOH roasting method proposed by authors, which is undergoing to scale up. The experimental titanium hydrolysis was detected by the infrared and Raman spectra for the first time to reveal the significant role of SO4 2− ions. The bridging bidentate SO4 2− ligands arrange the Ti–O octahedra of hydrated titanium dioxide (HTD) in zigzag chains along the crystal face (221) to form anatase structure and are changed into unidentate SO4 2− ligands and free bisulfate ions step by step with increasing hydrolysis time. This proposed mechanism of titanium hydrolysis in titanyl sulfate solution was applied to establish a new kinetic model x = 1 − k n e − k n ( 1 2 k m C Ti 0 + t ) 2 k m C Ti 0 [ E i ( k n t + k n 2 k m C Ti 0 ) − E i ( k n 2 k m C Ti 0 ) ] − e − k n t , which indicates the important effect of initial concentrations of titanium, sulfuric acid, and water on the titanium hydrolysis. The hydrolysis kinetic model is capable of describing the behavior of the system and can provide basic knowledge for scale-up of TiO2 production.


      PubDate: 2015-05-26T10:06:52Z
       
  • Ageing of polyethersulfone ultrafiltration membranes under long-term
           exposures to alkaline and acidic cleaning solutions
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Enrique Antón , José R. Álvarez , Laura Palacio , Pedro Prádanos , Antonio Hernández , Arto Pihlajamäki , Susana Luque
      Six commercial ultrafiltration membranes made of polyethersulfone from Microdyn Nadir, Koch Membrane Systems and GE Osmonics were exposed to 0.01, 0.1 and 1.0M nitric acid (HNO3) and sodium hydroxide (NaOH) solutions at 50°C for 150 days. Water permeability, molecular weight cut-off curves, ATR-FTIR, SEM-EDS, AFM and contact angle measurements were employed to evaluate membrane ageing. All membranes showed a high resistance to acidic solutions keeping their chemical and morphological properties almost invariant. The alkaline ageing did not induce any substantial change in the Nadir membranes but, the stability of Koch and GE Osmonics support layers was compromised at high NaOH concentrations, leading to even the complete degradation of these supports in some cases. This was confirmed by ATR-FTIR, SEM and GC–MS analysis. The Nadir membrane resistance to alkaline conditions was found to be in the support layer material composition (mixture of polyethylene and polypropylene). Koch and GE Osmonics membranes support material (polyethylene terephthalate) broke down into its monomers under strong alkaline conditions via hydrolysis reaction. Almost all membranes showed changes in membrane performance which were attributed to their conditioning or their degradation. Regardless of the cause, those changes took place mainly in the first 10 days of exposure. The influence of temperature on the ageing was also studied under the strongest alkaline condition. Its effect on chemically stable membranes were negligible whereas for the others, higher temperatures led to faster support layer degradation.


      PubDate: 2015-05-26T10:06:52Z
       
  • Initial reaction between CaO and SO2 under carbonating and non-carbonating
           conditions
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Martin Hagsted Rasmussen , Stig Wedel , Kim H. Pedersen , Jytte B. Illerup , Kim Dam-Johansen
      The initial kinetics of the CaO/SO2 reaction have been investigated for reaction times shorter than 1s and in the temperature interval between 450 and 600°C under both carbonating and non-carbonating conditions (0–20 vol% CO2) to clarify how recirculating CaO influences the emission of SO2 from a modern dry kiln preheater system for cement production. Calcined Faxe Bryozo limestone with a particle size smaller than 400μm was utilized as CaO source. It was shown, both theoretically and experimentally, that the observed reaction rates were influenced by mass transport limitations. The results showed that the CaO conversion with respect to SO2 declined when the CO2 concentration was increased. Under all conditions, larger specific surface areas of CaO gave higher reaction rates with SO2. Higher temperatures had a positive effect on the reaction between SO2 and CaO under non-carbonating conditions, but no or even a negative effect under carbonating conditions. The results led to the conclusion that SO2 released from raw meal in the upper stages of the preheater does not to any significant extent react with CaO recirculating in the preheater tower.


      PubDate: 2015-05-26T10:06:52Z
       
  • Characterization of oil–water two-phase pipe flow with a combined
           conductivity/capacitance sensor and wavelet analysis
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Chao Tan , Pengfei Li , Wei Dai , Feng Dong
      Flow patterns of horizontal oil–water two-phase pipe flow were studied with water holdup fluctuations provided by a set of conductivity and capacitance sensors. The in situ water fraction measured by the combined sensor was calibrated by quick-closing valves. Local wavelet energy (LWE) coefficients were extracted through continuous wavelet decomposition of the phase fraction history. The flow patterns in the horizontal pipe were identified visually and classified as water-continuous flow (oil dispersed in water flow, stratified flow with mixing at the interface, dispersion of oil in water and water flow and dispersion of water in oil, and oil in water flow) and oil-continuous flow (oil and dispersion of oil in water flow, and water dispersed in oil flow). The mechanics of flow behaviors of each flow pattern were interpreted from the LWE coefficient maps. Two features, the normalized LWE coefficient W ⁎ and the normalized scale a ⁎, were extracted from the LWE coefficient maps to represent changes in flow patterns. Using these two coefficients, the flow pattern transition with superficial flow velocity of water (J w ) and oil (J o ) was investigated. An overall flow pattern transition is characterized in a W ⁎ − a ⁎ map, where a “triangular” distribution of flow patterns is formed and the flow pattern transition can be characterized with the change in phase fraction and overall flow velocity.
      Graphical abstract image Highlights

      PubDate: 2015-05-26T10:06:52Z
       
  • Electrogenerated bubbles induced convection in narrow vertical cells: PIV
           measurements and Euler–Lagrange CFD simulation
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Rainier Hreiz , Lokmane Abdelouahed , Denis Fünfschilling , François Lapicque
      This paper addresses the two-phase flow hydrodynamics in Vertical Plane Electrode Reactors with Gas Electrogeneration, VPERGEs: (1) An experimental investigation of the hydrodynamics in a laboratory-scale VPERGE reactor – for three different current densities – was carried out. Flow visualisation with a high-speed camera, using the gas bubbles as tracers allowed particular flow features to be evidenced. Moreover, thanks to suitable pre- and post- processing tools, the gas velocity fields have been obtained using a PIV algorithm. Measurement errors related to the use of this technique are discussed. The calculated velocity fields provided an overall picture of the flow behaviour, and constitute a data base that can serve for the validation of future numerical results. (2) The two-phase flow was simulated using the two-way momentum coupling Euler–Lagrange CFD approach. Bubbles were considered to be injected slightly away from the electrodes, and not directly at the electrodes surfaces. The shift in the injection position was taken as the average radius of the bubbles. This slight offset of the bubble injection location allowed to obtain a numerical solution that is quasi-independent of the mesh size. CFD results were in good agreement with experimental data, and reproduced key flow features such as spreading of the bubble curtains and bubbles dispersion toward the centre of the reactor.


      PubDate: 2015-05-26T10:06:52Z
       
  • Influence of fluid-mechanical parameters on volumetric mass transfer
           coefficient in a spout–fluid bed with a draft tube
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Milena Knežević , Dragan Povrenović
      In order to apply a spout–fluid bed reactor with a draft tube for the nitrification process of wastewater treatment, the influence of fluid-mechanical parameters on volumetric mass transfer coefficient was analyzed. Experiments were carried out in a 1000mm high 2D semi-column with a draft tube. The draft tube had a cross section of 50×50mm2 and the annular region of the reactor had a cross section of 50×140mm2. The work described in this paper reports the influence of several fluid-mechanical parameters including liquid and gas flow rates, particle diameters and particle circulation on volumetric mass transfer coefficient, k L a . The liquid flow ranged from 3.5–4.5m3/h and gas flow ranged from 300 to 800L/h. The particles used were glass spheres with diameters of 3, 4, 5 and 6mm. Tap water and air were used as the liquid and gas phase, respectively. The experimental results have shown that particle circulation through the draft tube contributes to k L a increase as well as the increase in the particle diameter, the gas and liquid flow rates.


      PubDate: 2015-05-26T10:06:52Z
       
  • Split of two-phase plug flow with elongated bubbles at a microscale
           branching T-junction
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Seok Kim , Sang Yong Lee
      In the present work, the behavior of the elongated bubbles in two-phase plug flow at a microscale branching T-junction was studied both experimentally and numerically, and the effect of the bubble length on the split ratio of the gas flow to the branch was tested. The T-junction consists of a main, branch and a run with their cross section of 0.6mm×0.6mm. Air and water were taken as the test fluids and the instantaneous motion of the nose, body and the tail parts of the bubbles at the T-junction region was examined in detail. Only the body part appeared longer with the longer bubbles while the shapes (and volumes) of the nose and the tail parts remained unchanged. When the body part occupied the T-junction region, the volumetric flow rates of the gas to the branch maintained constant and became almost equivalent to the total volumetric flow rate to the branch. (Similarly, when a liquid slug occupied the T-junction region, the volumetric flow rate of the liquid to the branch appeared the same with the total volumetric flow rate to the branch.) On the other hand, the volumetric flow rates of the nose and the tail parts to the branch varied drastically with time due to the complicated flow patterns around them. Thus, for given flow rates of the gas and the liquid phases at the main, the flow mal-distribution was more likely to occur with the shorter bubbles because the relative portions of the nose and the tail are larger in a unit cell, which consists of a bubble and a liquid slug. Hence, for accurate prediction of the splitting behavior of the two-phase plug flow at branching T-junctions, the length information of the unit cell is essential in addition to the flow rate of each phase at the main.
      Graphical abstract image

      PubDate: 2015-05-26T10:06:52Z
       
  • Upscaling solute concentration transport equations of countercurrent
           dialyzer systems
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Chen Yang , Wang Qinglian , Jiadong Guo , Akira Nakayama , Ting Qiu
      The present paper aims at an upscaled description of solute concentration transport processes in countercurrent dialyzer systems by means of a porous media approach based on the volume averaging theory. In consideration of solute diffusion and ultrafiltration processes, a general set of upscaled solute concentration transport equations has been derived for the three phases in a hollow fiber dialyzer, namely, the blood, membrane and dialysate phases. Moreover, the corresponding closure problems, which can be solved to obtain the effective properties in the upscaled model, are proposed. For the one-dimensional case, analytical expressions of solute concentrations in both blood and dialysate phases are achieved, so as to elucidate the influences of ultrafiltration flow rate and distribution coefficient on both clearance enhancement and solute concentration variations along the length of dialyzer. The results show that both ultrafiltration flow rate and distribution coefficient have no significant effects on solute concentration variations along the length of dialyzer. Nevertheless, the clearance enhancement are found to have linear relationship with both ultrafiltration flow rate and distribution coefficient.


      PubDate: 2015-05-26T10:06:52Z
       
  • Visual investigation on the interface morphology of Taylor bubble and the
           characteristics of two-phase flow in mini-channel
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Qi Lu , Deqi Chen , Qinghua Wang
      A visual experimental investigation on Taylor bubble behavior of two-phase flow was carried out in vertical circular channels, with the length of 1000mm and inner diameter of 1mm, 2mm, 3mm and 6mm. Deionized water was used as the liquid-phase working fluid, and air, nitrogen, argon and carbon dioxide were adopted as the gas-phase working fluids. The interface morphology of Taylor bubble was recorded by a high speed camera, and the variations of pressure drop and liquid-phase mass flux were measured simultaneously. The effects of different working conditions on the interface morphology of Taylor bubble were discussed in detail, and the effect of surface tension on the Taylor bubble behavior was investigated based on the Eo (Eötvös) number and the Mo (Morton) number. Also, the fluctuations of pressure drop and liquid-phase mass flux were analyzed in detail based on the Taylor bubble behavior. Finally, a model for prediction of the two-phase flow pressure drop in mini-channel was proposed, and this model was validated based on the experimental result with good agreement.


      PubDate: 2015-05-26T10:06:52Z
       
  • Single stage H2 production, purification and heat supply by means of
           sorption-enhanced steam reforming of glycerol. A thermodynamic analysis
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Robert Wess , Federico Nores-Pondal , Miguel Laborde , Pablo Giunta
      The effect of CO2 removal with CaO in the production and purification of fuel cell-grade H2 by glycerol steam reforming is studied from a thermodynamic point of view. Results obtained with the non-stoichiometric method show that CaO enables some improvements to the conventional steam reforming since four simultaneous processes take place at the same stage: H2 production, CO2 separation, CO elimination and heat supply: by separating the CO2 from the gaseous mixture, CaO also shifts the equilibrium towards the production of H2 compared to conventional reforming, and the operating temperature is lowered with respect to conventional steam reforming. The removal of CO2 not only enables higher H2 purity (close to 100% on dry basis) but reduces the amounts of CO as well. For temperatures below ca. 750K, a level lower than 20ppm (on dry basis) can be reached, thus avoiding the need of a purification stage. Since the reaction of CaO with CO2 is exothermic, the heat is supplied within the reactor. Finally, it was found that the system behavior was strongly dependent on the presence of Ca(OH)2.This four-in-one process can be a way of enhancing the efficiency of the overall system of production–purification of H2.


      PubDate: 2015-05-26T10:06:52Z
       
  • Numerical and experimental investigation of dripping and jetting flow in a
           coaxial micro-channel
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Wenjie Lan , Shaowei Li , Guangsheng Luo
      The liquid–liquid two-phase flow in a coaxial micro-channel was investigated by computational fluid dynamics (CFD) simulations and online microscope. A modified level set method was used to simulate the free-surface flow. Two flow patterns, dripping flow and jetting flow were both successfully simulated. The experimentally recorded video for droplet formation is in good agreement with the simulation results. The flow pattern transition and droplet size variation were then investigated by changing the two phase viscosities and velocities. The simulated pressure distribution and velocity field for both the dripping and jetting flow revealed the dynamics of the droplet formation process. The pressure change at the dispersed phase entrance during a droplet formation period was studied based on the simulation results, which has not yet been reported in the literature to our knowledge. The simulated pressure of dripping flow was then compared to experimental measurement and good agreement was obtained. The simulation results further revealed the intrinsic difference between the dripping and jetting flow. Numerical simulation provides a supplementary method to study the details in the micro-scale flow, which is difficult to be studied by experiments.


      PubDate: 2015-05-26T10:06:52Z
       
  • Experimental study on oscillation behaviors in T-jets reactor with
           excitation
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Gong-yi Tu , Wei-feng Li , Wen-wei Qian , Zhe-hang Shi , Hai-feng Liu , Fu-chen Wang
      The oscillation behaviors in T-jets reactors with excitation are experimentally studied by a flow visualization technique. The images of the smoke-seeded flow are captured by a particle imaging velocimetry (PIV) system and a high-speed camera. The effects of the Reynolds number, the excitation frequency and the excitation amplitude on the oscillation behaviors in T-jets reactors have been investigated. The impingement plane flaps periodically caused by the pulsed inflow, and the excited flapping frequencies of the impingement planes are equal to the excitation frequencies. Different oscillation behaviors in T-jets reactors with excitation are identified, and the interaction between the self-sustained oscillations and the excited flapping oscillations is investigated and discussed. Results show that the excitation as well as the geometry parameters of T-jets reactors has significant effects on oscillation behaviors. The excited oscillation amplitudes of impingement planes increase with Reynolds numbers and excitation amplitudes, but non-monotonically decrease with excitation frequencies.


      PubDate: 2015-05-26T10:06:52Z
       
  • Fully coupled TFM-DEM simulations to study the motion of fuel particles in
           a fluidized bed
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): F. Hernández-Jiménez , L.M. García-Gutiérrez , A. Soria-Verdugo , A. Acosta-Iborra
      In the present work, novel numerical simulations using a hybrid model are carried out to study the motion of objects, representing fuel particles, in a pseudo-2D fluidized bed. The hybrid model combines the continuum treatment of the gas phase with the possibility to treat different solid phases either as continuum, or discrete. In the present case, both the gas and the dense phase of the bed are modelled as continuum phases, as typically done in two-fluid model simulations, whereas fuel particles are simulated as discrete entities whose movement affects, and can be affected by the dense phase motion (i.e. fully coupled TFM-DEM simulations). The results obtained from the model are qualitatively and quantitatively compared with reported experimental findings available in the literature. Firstly, the motion of the fuel particle with regards to the bubble phase and dense phase is proved to be realistic. Secondly, the location probability of the particle in the simulated bed is calculated and compared with the experimental data. Then, the ballistic path followed by the particle in the freeboard is also compared with experimental measurements. These results show good agreement between experiments and simulation. The numerical results reflect the same behaviour during the ascending and descending motion of the fuel particles as that observed in the experiments. The results also show that the most probable locations of the particles predicted by the simulations are consistent with the experimental findings, both inside the fluidized bed and in the freeboard. Overall, the hybrid model tested shows quite promising results, which indicates the potential usability of the model.
      Graphical abstract image Highlights

      PubDate: 2015-05-26T10:06:52Z
       
  • Analysis of water-using networks with multiple contaminants involving
           regeneration recycling
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Ai-Hong Li , Yu-Zhen Yang , Zhi-Yong Liu
      The introduction of regeneration recycling unit can significantly reduce freshwater consumption and consequently reduce wastewater discharge of water-using systems. In this paper, the influences of the regenerated concentrations of contaminants on regenerated stream consumption are investigated for the fixed mass-load water networks with multiple contaminants. The multi-contaminant water networks involving regeneration recycling are classified into simple ones and complex ones in this paper. Simple networks are similar to single-contaminant ones, in which only the key contaminant limits the usage of regenerated water. The regenerated stream consumption of simple networks can be predicted easily when the regenerated concentration of the key contaminant changes. The concentrations of other contaminants, if having influence on the regenerated stream consumption as well, should be reduced to their maximum allowable values. There is great difference between the features of complex networks of multiple contaminants and that of networks of single contaminant. The influence of the regenerated concentrations on regenerated stream consumption of complex networks is analyzed based on mass balances of the contaminants. The contaminant which has the most influence on regenerated stream consumption is identified. The methods proposed can contribute to evaluation of the appropriate regenerated concentrations for design or retrofit of the water networks with multiple contaminants.


      PubDate: 2015-05-26T10:06:52Z
       
  • Dihydroxyacetone crystallization: Process, environmental, health and
           safety criteria application for solvent selection
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Juan F. Martínez-Gallegos , Alejandro Burgos-Cara , Francisco Caparrós-Salvador , Germán Luzón-González , Mercedes Fernández-Serrano
      Dihydroxyacetone is a good candidate to valorize the excess glycerol obtained as byproduct in biodiesel production. Crystallization is likely the key unit operation to obtain a high quality and pure dihydroxyacetone. The selection of an appropriate solvent for crystallization is not trivial and depends on multiple factors. At the present work a new solvent selection methodology, based on solvents relative comparisons, is described and applied to dihydroxyacetone crystallization as a case study. The procedure accounts not only for process factors such as solubility and yield, but also for cost, recycling, disposal, environmental, health and safety issues. Solubility and theoretical yield data for dihydroxyacetone in methanol, ethanol and 2-propanol were experimentally determined, while cost, life-cycle assessment, environmental, health and safety data of solvents were gathered from different bibliographic sources, software and databases. Among the solvents assessed, methanol resulted as the best overall choice for DHA crystallization. The methodology proved to be a suitable, simple and flexible procedure for solvent selection at the initial stages of the crystallization operation design, being able to be upgraded for advanced stages of the crystallization process development.


      PubDate: 2015-05-26T10:06:52Z
       
  • Bayesian improved model migration methodology for fast process modeling by
           incorporating prior information
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Linkai Luo , Yuan Yao , Furong Gao
      We consider a Bayesian inference approach to enhance model migration, building on concepts laid out in an earlier paper (Lu and Gao, 2008a). Previous studies have been limited to a least-squares solution and have failed to take prior knowledge into consideration, possibly tending to cause overfitting and inaccurate estimations. We present a framework for Bayesian migration that can naturally incorporate and use prior information. The approach involves imposing normal-inverse-gamma priors over the migration parameter and exploring the resulting posterior distributions using a Markov chain Monte Carlo method. In addition, we provide a batch sequential design framework for iterative implementation of model migration, which thus avoids an exhaustive treatment of a predetermined number of design points. The effectiveness of these proposed methods is demonstrated using two examples: a numerical study and an injection molding process.


      PubDate: 2015-05-26T10:06:52Z
       
  • Transient rotating electromagnetohydrodynamic micropumps between two
           infinite microparallel plates
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Yongjun Jian , Dongqing Si , Long Chang , Quansheng Liu
      By using the method of separation of variables, analytical investigations are performed for combined transient rotating electromagnetohydrodynamic (EMHD) flow of an electrically conducting, incompressible and viscous fluid between two slit microparallel plates. The flow relies on the rotating effect and the Lorentz force produced by the interaction between an externally imposed electrical current and a transverse magnetic field. Three different cases associated with electric and magnetic fields are discussed respectively, i.e., uniform electric and magnetic fields (case I); AC electric field and uniform magnetic field (case II); AC electric and magnetic fields (case III). The variations of velocity profiles and volume flow rates with time and their dependence on the rotating Reynolds number ReΩ and the Hartmann number Ha are explained graphically. The results show that the magnitude of rotating EMHD velocity increases with Ha within a range when Ha<3 in our present analysis. With the increase of the rotating Reynolds number, the magnitude of rotating EMHD velocity decreases in axial direction and increases in lateral direction. For small rotating Reynolds number ReΩ, an interesting phenomenon for case I is that the maximum is not shifted and the maximum of the velocity in axial direction is the minimum of the velocity in lateral direction, and vice versa. However, there is a shift of the maximum for large rotating Reynolds number ReΩ. Under the case II and the case III, the periodic oscillating phenomenon of the rotating EMHD velocity occurs. In addition, for three cases, the flow rate in y ⁎ direction increases with Hartmann number and decreases with rotating Reynolds number. The amplitude of EMHD velocity is larger under the case II than that of steady solution under case I, but smaller than that under case III for prescribed Hartmann number Ha and rotating Reynolds number ReΩ. Interestingly, there is a giant augmentation of the flow rates both in axial and in lateral directions for case III due to the aiding part of Lorentz force being greatly larger than retarding one in certain parameter ranges of phase of the magnetic field relative to the electrical field. By comparing our theoretical results in the limit case without rotation effect with related experimental data, the analytical results coincide qualitatively with the fitted curve obtained in experiments.
      Graphical abstract image

      PubDate: 2015-05-26T10:06:52Z
       
  • Absolute and convective instabilities in double-diffusive two-fluid flow
           in a slippery channel
    • Abstract: Publication date: 29 September 2015
      Source:Chemical Engineering Science, Volume 134
      Author(s): Sukhendu Ghosh , R. Usha , Kirti Chandra Sahu
      Spatio-temporal instability of miscible two-fluid symmetric flow in a horizontal slippery channel is considered. Both fluids have the same density but different viscosity. A smooth viscosity stratification is created by a thin mixed layer between the fluids due to the presence of two species/scalars, which are diffusing at different rates. Our study suggests the existence of a rapidly growing absolute unstable mode for higher viscosity ratio with a highly viscous fluid close to the slippery channel wall. This instability is less stronger in the case of the equivalent single component two-fluid flow. The viscosity stratified single component (SC) and double-diffusive (DD) slippery flows are absolutely unstable for a wide range of parameter values, when a highly viscous fluid is adjacent to the slippery wall and the mixed layer is close to the channel wall with slip. The instability can be either enhanced or suppressed by wall slip and this is dependent on the location of mixed layer, inertial effects, diffusivity and the log-mobility ratios of the faster and slower diffusing species. This suggests that one can achieve early transition to turbulence due to the absolute instability in a viscosity stratified channel flow by making the channel walls hydrophobic/rough/porous with small permeability, which can be modelled by the Navier-slip condition.


      PubDate: 2015-05-26T10:06:52Z
       
 
 
JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
 
About JournalTOCs
API
Help
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2015